Top feed mechanism for sewing machines

ABSTRACT

A top feed mechanism which can be incorporated conveniently in sewing machines not originally designed for top feeds. The top feeding foot is slidably pivoted in the machine frame between the conventional presser bar and needle bar and is lifted and lowered by a linkage supported on a plunger telescopically arranged in the presser bar so that the presser foot will not be elevated during the feed stroke of the top feeding mechanism.

Patented March 16, 1971 INVENTOR Eerie C. Kunes ATTORNEY WITNESS 7 par/rwa TOP? FEED MEQHANISM FOR SEWING MAiCHlINES BACKGROUND OF THE INVENTION This invention relates to work-feeding mechanism for sewing machines, and more particularly, to a top feeding mechanism in which a work-feeding foot operates through slots in a presser foot and is alternately lowered into engagement with the work and moved in a feed stroke to advance the work, and elevated out of engagement with the work and returned.

in those sewing machines which have heretofore included top feeding mechanisms, the design of the machine including the machine frame has been made with accommodation of the top feed mechanism in mind; so that machines with top feed mechanisms have heretofore been special machines involving increased expense.

It is an object of this invention to provide a top feed mechanism which may be included readily in a sewing machine that is not designed originally to accommodate a top feeding mechanism.

Another object of this invention is' to provide a top feeding mechanism of the above character in which the operation of the top feeding mechanism does not entail raising of the sewing machine presser foot during the active or work-feeding stroke of the top feed dog.

The above and additional objects of this invention are attained by the provision of a top feeding mechanism in which the top feed dog is carried by a feed bar which is slideably pivoted in a bearing sleeve which is journaled on an axis transversely of and between the presser and needle bars of the sewing machine. The top feed bar is alternately raised and lowered by a linkage which is carried by a pivotal connection with a plunger telescopically accommodated in a bore in the presser bar. When this top feed bar raising linkage is operated by the sewing machine, the linkage supported by the plunger can lift the top feed bar when the plunger bottoms in the presser bar bore, but when driven in the opposite direction the linkage cannot lift the presser bar and instead merely elevates the plunger in the presser bar bore. An advantage of this arrangement is in the reduction of vibration and inertial forces occasioned by an absence of lifting and lowering of the presser foot with the result that the mechanism of this invention becomes particularly suitable for higher speeds of sewing machine operation.

DESCRIPTION OF THE DRAWINGS A preferred embodiment of the top feeding mechanism of this invention is illustrated in the accompanying drawing in which:

The FIGURE represents a perspective view of the presser bar and needle bar of a sewing machine together with the bearings, therefor, and the operating parts of a top feeding mechanism in accordance with this invention, all arranged in the relative position which the parts would occupy when assembled in a conventional sewing machine head, but with the sewing machine frame omitted more clearly to illustrate the parts.

Illustrated at ill in the drawing is a sewing machine needle bar which is endwise reciprocable in needle bar bearings 12 and 13 which, as conventional, are secured in the frame of a sewing machine (not shown). A drive stud 14 secured by means of a split clamp 15 on the needle bar provides for a driving connection to the needle bar from conventional needle reciprocating mechanism in the sewing machine.

Spaced in substantially parallel relation to the needle bar in a bearing 16 in the sewing machine frame is a presser bar 17 which is preferably of the conventional type having an axial bore 18 which in the usual sewing machine construction accommodates the presser spring which biases the presser bar toward a work-supporting surface of the sewing machine. As will be described herein below, the presser bar bore in the present invention is used for a different purpose i.e., in respect to the support of actuating mechanism for the top feed mechanism. Clamped to the lower extremity of the presser bar is the shank portion 19 of a presser foot indicated generally at 20. The presser foot preferably includes a work-engaging shoe 21 formed with a needle-accommodating slot 22 and with a pair of top-feed-dog-accommodating slots 23 and 24. Above the presser bar bearing to a block 25 may be secured to the presser bar 17 to accommodate connections with any conventional presser foot lifting linkage. A block 26 may also be secured to the presser bar 17 and provide connection with a rearwardly and upwardly extending tang 27 which serves the dual function of cooperating with a guide means on the sewing machine frame to prevent turning of the presser bar and also by way of an upstanding pin 28 thereon to accommodate the presser-bar-biasing spring 294. The downward force of the spring exerted on the presser bar may be regulated by an adjusting screw 30 threaded into the sewing machine frame.

The presser bar and needle bar parts described above may be conventional in construction and it is a feature of this invention that the top feeding mechanism which will now be described is particularly adapted for accommodation in a machine having originally the conventional needle bar and presser bar arrangement described above. Journaled in the sewing machine frame between the needle bar and presser bar on an axis perpendicularly transverse thereof is a bearing cylinder to which a bearing sleeve 42 is clamped by means of a set screw 41. Endwise slideably carried in the bearing sleeve 42 is a feed bar 43 formed at the top with a clevis 44 and having secured at the bottom a feed foot 45 preferably formed with spaced feeding blades 46 and 47 which work in the feeddog-accommodating slots 23 and 24 of the presser foot.

The feed and return movements are imparted to the feed dog by imparting oscillatory movement to the bearing sleeve 42, and the feed dog is lifted out of engagement with the work during each return movement and lowered into engagement with the work during each feed movement by mechanism attached to the clevis 44 for shifting the feed bar 43 axially in the bearing sleeve. For oscillating the bearing sleeve 42 an operating arm 50 is secured to the bearing sleeve and is pivotally connected by a pin 51 to a link 52 which is in turn pivoted by a pin 53 to a rock arm 54 clamped to the inner rock shaft 55 of a pair of telescopically arranged rock shafts 55 and 56 which are journaled in the machine frame.

The outer rock shaft 56 serves to impart lifting and lowering movements to the feeding foot and to this end has secured thereon a rock frame preferably including spaced rock arms 58. The spaced rock arms 58 have associated therewith identical linkages connected to the clevis 4% so that the space therebetween can be provided for the tang 27 which transmits spring pressure to the presser bar. The space between the linkage parts for the feeding foot lift mechanism also provide a particularly advantageous support for the linkage relatively to the presser bar as will be described below. Pivoted on pins 59 to each of the rock arms 58 are links 60 pivoted by pins 61 in turn to the upstanding extremities of bellcranks 62 which are pivotally connected by a pin 63 at the other extremity to a block 64 which is pivoted by a pin 65 to the clevis 44. Each of the bellcranks 62 accommodates a fulcrum pin 66 which passes through a plunger rod 67 which is slideably in the axial bore lift! of the presser bar. Threaded in the sewing machine frame adjacent to the presser spring adjusting screw 30 is an adjusting screw 69 for the feeding foot. The adjusting screw 69 accommodates an upstanding pin 70 which is associated with a shoe 71 preferably placed to straddle the block 64 which connects the bellcranks 62 with the clevis 44 on the feed bar. A coil spring 72 constrained on the pin 70 is regulated by the adjusting screw 69 to bias the feed bar 43 downwardly. When the rock shaft 56 is oscillated in a clockwise direction, as illustrated in the drawing, the bellcranks s2. will be turned about the fulcrum pin 66 so as to elevate the feeding foot and in so doing the plunger rod 67 will bottom in the presser bar bore 18 and the force of the feed-biasing spring 72 will be transferred by the bellcranks 62 to the presser bar. When the rock shaft is turned in a counterclockwise direction and the bell cranks are turned in the opposite direction, the feeding foot will be lowered into the engagement with the work and the pin 63 will become the fulcrum for the turning movement of the bellcranks 62 as soon as the feed dog contacts the work. Additional movement of the bellcranks 62 then will serve to elevate the plunger rod 67 relatively to the presser bar but the presser foot will not be lifted from the work. The presser spring 29 will continue to bias the presser foot downwardly and the feedbiasing spring 72 will be applied to the feeding foot and will not be transferred to the presser foot during the feeding stroke of the feed dog. By this construction a top feeding mechanism is provided which is well suited for use in modern high-speed sewing machines because of the absence of objectionable inertia forces resulting from elimination of the necessity for raising the presser foot at each stitch. The mechanism of this invention also provides a compact arm which can be incorporated readily into existing designs of machine frames not originally made with a view toward accommodating a top feed mechanism.

I claim:

1. ln a sewing machine having a driving mechanism, a frame, a work presser, and a work-presser-carrying bar and a needle-carrying bar supported in substantially parallel relation in said sewing machine frame, a top feeding mechanism com prising a top feed bar slideably pivoted on said sewing machine frame between said presser and needle carrying bars, a feed dog carried by said top feed bar, mechanism driven by said sewing machine driving mechanism for causing pivotal movement to said feed bar to impart feed and return movements to said feed dog, and lift mechanism driven by said sewing machine driving mechanism for lifting said top feed bar during each return movement of said feed dog, said feed lift mechanism including a member mounted on and shiftable along said presser carrying bar, stop means limiting movement of said member toward said work presser, and a lever operatively connected for oscillation by said sewing machine driving mechanism and having spaced pivotal connections to said member and to said top feed bar.

2. A top feeding mechanism as set forth in claim 1 in which said feed lift mechanism lever comprises a bellcrank one arm of which has one of said pivotal connections with said top feed bar, and in which said stop means comprises a blind axial bore in said presser carrying bar and said member shiftable along said presser carrying bar comprises a plunger rod slideably accommodated in said blind axial bore and having the other of said pivotal connections with said bellcrank between the extremities thereof. 

1. In a sewing machine having a driving mechanism, a frame, a work presser, and a work-presser-carrying bar and a needlecarrying bar supported in substantially parallel relation in said sewing machine frame, a top feeding mechanism comprising a top feed bar slideably pivoted on said sewing machine frame between said presser and needle carrying bars, a feed dog carried by said top feed bar, mechanism driven by said sewing machine driving mechanism for causing pivotal movement to said feed bar to impart feed and return movements to said feed dog, and lift mechanism driven by said sewing machine driving mechanism for lifting said top feed bar during each return movement of said feed dog, said feed lift mechanism including a member mounted on and shiftable along said presser carrying bar, stop means limiting movement of said member toward said work presser, and a lever operatively connected for oscillation by said sewing machine driving mechanism and having spaced pivotal connections to said member and to said top feed bar.
 2. A top feeding mechanism as set forth in claim 1 in which said feed lift mechanism lever comprises a bellcrank one arm of which has one of said pivotal connections with said top feed bar, and in which said stop means comprises a blind axial bore in said presser carrying bar and said member shiftable along said presser carrying bar comprises a plunger rod slideably accommodated in said blind axial bore and having the other of said pivotal connections with said bellcrank between the extremities thereof. 